An optical layered body including function layers with various functions such as antireflection properties and antistatic properties is generally provided on the outermost surface of image display devices such as cathode-ray tube (CRT) display devices, liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), field emission displays (FEDs), touch panels, and electronic paper.
As one of such function layers of the optical layered body, an antistatic layer for presenting adhesion of dust and dirt caused by static electrification is known (for examples, see Patent Literatures 1 to 5).
The antistatic layer is generally forced by using an antistatic agent. Known examples of the antistatic agent include metal oxide-based conductive ultrafine particles such as antimony-doped tin oxide (ATO) and tin-doped indium oxide (ITO), organic conductive polymers, and quaternary ammonium salt-based conductive materials. Of these, quaternary ammonium salts are often used these days as coating-type antistatic agents. For example, Patent Literature 6 discloses a cationic copolymer having a quaternary ammonium salt group with an excellent solubility in hydrophobic solvents and resin.
As another function layer, a hard coat layer for providing a certain degree of strength to the optical layered body is also known.
Such an antistatic layer and a hard coat layer provided on the optical layered body have been formed as separate layers on respective transparent substrates (for example, see Patent Literature 7).
Therefore, steps for separately forcing an antistatic layer and a hard coat layer were necessary, thus disadvantageously increasing the production process and the production cost of the optical layered body.
In response to these problems, fox example, a hard coat layer and an antistatic layer may possibly be formed as a single layer by adding an antistatic agent to the hard coat layer, as a method for simplifying the production process in order to reduce the production cost of the optical layered body.
However, there have been problems: imparting sufficient antistatic properties to the hard coat layer reduced the transparency of the hard coat layer, while imparting sufficient transparency to the hard coat layer resulted in insufficient antistatic properties. Additionally, imparting sufficient antistatic properties to the hard coat layer disadvantageously resulted in insufficient adhesion of the hard coat layer to another layer provided thereon.
As described above, when the hard coat layer and the antistatic layer are formed as a single layer, it has been difficult to obtain an optical layered body having excellent antistatic properties, optical characteristics, and adhesion to other layers.